The Houthi rebels in Yemen, officially known as Ansurallah, have vowed to intensify rocket attacks on Saudi Arabia’s critical oil infrastructure, warning that they are now manufacturing their own ballistic missiles to achieve those aims, the Financial Times reports.

The threat comes at a time when Houthi attacks on Saudi Arabia have begun to increase. Just this Saturday, Saudi Arabia’s air defense system intercepted four ballistic missiles over the southwestern region of Jizan. The debris of those missiles reportedly killed one person. Just a week prior, two other missiles were launched at the Saudi Arabian Oil Company (Aramco) facilities on the Red Sea.

At the beginning of April, the London-based IHS Jane’s Terrorism and Insurgency Center noted that the Houthis claimed to have carried out three separate rocket attacks on Aramco facilities in ten days, including an attack on a Saudi oil tanker, which suffered some damage and led to the intervention of a coalition naval vessel, which in turn repelled the attack.

The Houthis also unveiled their new Badr-1 surface-to-surface weapon system (a heavy artillery rocket system) approximately a week prior, which the rebels claimed they had used to attack Aramco facilities.

Mohammed al-Boukhaiti, a member of the Houthi political council, also told the Financial Times that these attacks were “only the beginning of the response” to the death of Houthi leader Saleh al-Samad, who was killed by Saudi air strikes in April.

“Yemenis will not pass on the death of Samad easily and they will do their best to take revenge for him,” Mr. Boukhaiti said.

Boukhaiti also dismissed allegations that Iran has supplied the Houthis with sophisticated missiles, claiming instead that the rebels have been developing and manufacturing their own rockets and drones.

“The Yemenis have added new systems for manufacturing missiles, so more missiles are targeting Saudi Arabia as a part of an escalation,” Mr. Boukhaiti also said.

Despite this, these recent developments are raising fears that the war in Yemen may begin to spiral out of control even more so than it has already in the last three years. As even the Financial Times admits, so far into the conflict Saudi Arabia has struggled to make any decent advancement against the rebels. It is also worth noting that in recent times, the Houthis’ confidence only appears to be strengthening, and these recent attacks targeting vital Saudi infrastructure may only improve their standing in the conflict.

According to Graham Griffiths, a consultant with Control Risks Group, these Houthi-led attacks have raised concerns for the safety of employees and assets even if the Houthis cannot exact any significant damage to the Saudi-led coalition.

“This perception of the risk is likely to greatly increase if even a single strike hits a sensitive target,” Griffiths said, according to the Financial Times. “The sustained pace of the attacks allows the Houthis to demonstrate that despite three years of war, they can still retaliate against a much more powerful foe.”

Most importantly — and largely missing from any serious analysis of this conflict — is Mr. Boukhaiti’s statement to the Financial Times that the Houthis will continue these attacks on Saudi Arabia until Riyadh “stops its aggression completely.”

As far as international law is concerned, Yemen is entitled to the right to defend itself from foreign aggression, including striking directly at Saudi Arabia, which is by all accounts the principal instigator of this conflict.

One might be inclined to believe a simple solution worth pursuing would be for the Saudi-led coalition to withdraw from its aggressive and criminal war in Yemen and allow Yemenis to conduct their own affairs.